The search for the molecule or molecules responsible for the formation, proliferation, differentiation and maintenance of tissue and organs, such as cartilage and connective tissues, has been extensive as there is a tremendous need for factors useful for treating conditions involving degradation or damage to these tissues, such as osteoarthritis.
The structures of several proteins in the family designated as Frizzled, have previously been elucidated. The present invention relates to a family of proteins designated as Frazzled, which family shares homology to the ligand binding domain of the Frizzled proteins. Frizzled protein family members have been shown to bind to the Wingless (Wg) protein in Drosophila. Bhanot et al., Nature, 382:225–230 (1996). In mammals and other species, the Frizzled family of proteins are membrane bound receptor molecules which have been shown to bind to proteins produced by the family of Wnt genes. Wang et al., J. Biol. Chem., 271:4468–4476 (1996). Wnt genes have been determined to be expressed in tissue and organs including the pancreas, lung, liver, kidney, and brain.